Ligand Adducts of Bis(acetylacetonato)iron(II): A 1H NMR Study
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- 作者：Zhigang Xue ; Jean-Claude Daran ; Yohan Champouret ; Rinaldo Poli
- 刊名：Inorganic Chemistry
- 出版年：2011
- 出版时间：November 21, 2011
- 年：2011
- 卷：50
- 期：22
- 页码：11543-11551
- 全文大小：425K
- 年卷期：v.50,no.22(November 21, 2011)
- ISSN：1520-510X
文摘
We report here a thorough 1H NMR study of Fe(acac)2 solutions in a wide variety of noncoordinating and coordinating solvents, as well as the interaction of this complex with Et3N, pyridine, PMe2Ph, and R2PCH2CH2PR2 [R = Ph (dppe), Et (depe)] in C6D6. The study reveals that Fe(acac)2 is readily transformed into Fe(acac)3 in solution under aerobic conditions and that the commercial compound is usually contaminated by significant amounts of Fe(acac)3. The 1H NMR resonances of Fe(acac)2 are rather solvent-dependent and quite different than those reported in the literature. The compound is unstable in CDCl3 and stable in CD2Cl2, C6D6, CD3CN, acetone-d6, DMSO-d6, THF-d8, and CD3OD. The addition of the above-mentioned ligands (L) reveals only one paramagnetically shifted band for each type of acac and L proton, the position of which varies with the L/Fe ratio, consistent with rapid ligand exchange equilibria on the NMR time scale. A fit of the NMR data at a high L/Fe ratio allows the calculation of the expected resonances for all protons in the Fe(acac)2L2 molecules. The system with the bidentate depe ligand shows evidence for a slow ligand exchange at low depe/Fe ratios, proposed to involve a species with the cis-chelated mononuclear Fe(acac)2(depe) structure, whereas the fast exchange at a higher ratio is proposed to involved a trans-Fe(acac)2(魏1-depe)2 complex. Complex Fe(acac)2(dppe) cannot be investigated in solution because of low solubility in a noncoordinating solvent and because of the poor dppe competition for binding in coordinating solvents. The compound was crystallized, and its X-ray structure reveals a 1-dimensional polymeric structure with dppe-bridged Fe centers having the trans-octahedral Fe(acac)2(魏1-dppe)2 coordination environment.